High-frequency input/output feedthrough and package for housing high-frequency semiconductor element using same

ABSTRACT

A high-frequency input/output feedthrough comprises a lower dielectric substrate in which are formed a bottom face ground layer, side ground layers, a line conductor and cofacial ground layers (formed on both sides of the line conductor on one and the same face of the lower dielectric substrate); and an upper dielectric substrate joined to the lower dielectric substrate so that portions of the line conductor and cofacial ground layers are sandwiched between the lower and upper dielectric substrate. In order to suppress return and insertion losses of signal in millimeter wave range due to a difference in transmission mode to improve transmission characteristics, the upper dielectric substrate is made thicker than the lower dielectric substrate. The width of the portion of the line conductor which is sandwiched between the lower dielectric substrate and the upper dielectric substrate is smaller than that of another portion. The cofacial ground layers are projected toward the line conductor. The transmission modes for high-frequency signals are matched, so that the return and insertion losses can be reduced and excellent transmission characteristics of high-frequency signals can be attained.

This is a division of application Ser. No. 09/031,402 filed Feb. 26,1998 now U.S. Pat. No. 6,043,556, which application is herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a high-frequency input/outputfeedthrough for a package for housing a high-frequency semiconductorelement for the millimeter wave region or the like, and also to apackage for housing a high-frequency semiconductor element and using thehigh-frequency input/output feedthrough.

2. Description of the Related Art

A package for housing a high-frequency semiconductor element houses ahigh-frequency semiconductor element using a high-frequency signal inthe micrometer wave region, the millimeter wave region, or the like, ina hermetically sealed manner. A signal input/output portion of such apackage employs a feedthrough structure to which a transmission linesuch as a microstrip line or a stripline is joined and which ishermetically sealed while a semiconductor element is housed in thepackage.

An example of the configuration of such an input/output feedthrough isshown in FIGS. 19A, 19B, and FIG. 19A is a plane view and FIG. 19B is asectional view taken along line I—I of FIG. 19A, in which lowerdielectric substrate 1 is made of ceramics or the like. An upperdielectric substrate 2 is made of ceramics or the like and joined to theupper face of the lower dielectric substrate 1, and serves as a part ofa case wall of a package. A line conductor 3 is formed on the upper faceof the lower dielectric substrate 1. Side face ground layers 4 areformed on the side faces of the lower and upper dielectric substrates 1and 2. A bottom face ground layer 5 is formed on the bottom face of thelower dielectric substrate 1. An upper-face ground layer 6 is formed onthe upper face of the upper dielectric substrate 2. The prior art ofFIG. 7 is the configuration of an input/output feedthrough used forso-called metal wall type packages.

According to this input/output feedthrough, the matching of thecharacteristic impedance of the line conductor 3 is attained by changingthe line width of the portion sandwiched between the lower dielectricsubstrate 1 and the upper dielectric substrate 2 and corresponding tothe stripline, with respect to that of the portions in front and in rearof the portion and corresponding to a microstrip line, thereby realizinglow return and insertion losses. When an input/output feedthrough havingthe bottom face ground layer 5 and the side face ground layers 4 on thesides of the dielectric substrates 1 and 2 is embedded in a cutaway partformed in a metal substrate of the package, the isolationcharacteristics between the line conductor 3 and a line conductor ofanother input/output feedthrough which is juxtaposed to the lineconductor 3 are improved.

In another input/output feedthrough, a ground pattern is disposed onboth sides of a line conductor as shown in FIGS. 20A and 20B. FIG. 20Ais a plane view, and FIG. 20B is a section view taken along line II—II.Referring to these figures, a lower dielectric substrate 7, an upperdielectric substrate 8, a line conductor 9, a bottom face ground layer10, and an upper-face ground layer 11 are configured in the same manneras the lower dielectric substrate 1, the upper dielectric substrate 2,the line conductor 3, the bottom face ground layer 5, and the upper-faceground layer 6 of FIG. 19, respectively. Ground patterns 12 are formedon the lower dielectric substrate 7 so as to laterally sandwich the lineconductor 9. Through conductors 13 are through hole conductors or thelike through which the ground patterns 12 are connected to the bottomface ground layer 10. Through conductors 14 are through holes or thelike through which the ground patterns 12 are connected to theupper-face ground layer 11. The prior art of FIG. 20 has theconfiguration of an input/output feedthrough used for the so-calledceramic wall type packages. According to this input/output feedthrough,in the same manner as the input/output feedthrough shown in FIG. 19, thematching of the characteristic impedance of the line conductor 9 isattained so as to realize low return and insertion losses. Furthermore,the isolation characteristics are improved by surrounding the lineconductor 9 with the ground patterns 12, the through conductors 13 and14, the bottom face ground layer 10, and the upper-face ground layer 11.

In each of the high-frequency input/output feedthroughs, the lowerdielectric substrate 1 or 7 and the upper dielectric substrate 2 or 8which constitute the stripline portion are usually made of the samedielectric material and configured as dielectric members having asubstantially same thickness.

According to such a high-frequency input/output feedthrough of the priorart, in the region (the microwave region) wherein the frequency isrelatively low among high frequencies, the transmission characteristicsfor a high-frequency signal are excellent because the characteristicimpedance of the microstrip line portion is matched with that of thestripline portion.

However, for example, in a higher frequency region wherein the frequencyis higher than 30 GHz (the millimeter wave region) there arises thefollowing problem. In order to match the characteristic impedance of theline conductor 3, 9 in the stripline portion with that in the microstripline portion and further suppress a higher order modes, it is necessaryto decrease the thickness of the lower dielectric substrate 1, 7 andadditionally, since a width d1 of the line conductor in the striplineportion is very small and an unstable state is brought, it is necessaryto set a length d2 of the line conductor 3, 9 in the stripline portionto 1/2n (n is a natural number) of the wavelength of a high-frequencysignal to be transmitted via the input/output feedthrough, with theresult that the length d2 of the line conductor 3, 9 in the striplineportion becomes very short. Consequently, the strength of theinput/output feedthrough part is extremely lowered. Even when the lengthis designed to be 1/2n of the wavelength, the transmission mode in thestripline portion is substantially different from that in the microstripline portions in front and in rear of the stripline portion because theinput/output feedthrough part has a complex three-dimensional shape andthe shape is dispersedly produced. This produces a further problem inthat the return and insertion losses are increased and the transmissioncharacteristics for a high-frequency signal are impaired.

The configuration shown in FIG. 8 has further problems in that it isdifficult to produce the input/output feedthrough because the smallthrough conductors 13, 14 must be formed in the dielectric substrates 7and 8, and that, because of the shield due to the through conductors,the return and insertion losses are larger as compared with the case ofa planar shield.

SUMMARY OF THE INVENTION

The invention has been conducted in view of the above-discussedproblems. It is an object of the invention to provide a high-frequencyinput/output feedthrough having excellent transmission characteristicsin which the transmission mode for a high-frequency signal in a portioncorresponding to a microstrip line is matched with that in a portioncorresponding to a stripline portion to reduce the return and insertionlosses.

It is another object of the invention to provide a package for housing ahigh-frequency semiconductor element having excellent transmissioncharacteristics in which, in an input/output feedthrough part, thetransmission mode for a high-frequency signal in a portion correspondingto a microstrip line is matched with that in a portion corresponding toa stripline, to reduce the return and insertion losses.

In a first aspect of the invention, a high-frequency input/outputfeedthrough comprises:

a) a first dielectric substrate 15;

b) a high-frequency transmission line 19 of narrow width extending onone surface of the first dielectric substrate, the high-frequencytransmission line having a first high-frequency transmission lineportion 19 a and second high-frequency transmission line portions 19 b,19 c extending from both longitudinal ends of the first high-frequencytransmission line portion, respectively;

c) a pair of first ground conductors 20 of narrow width extending on theone surface of the first dielectric substrate, the first groundconductors being spaced from both width direction sides of thehigh-frequency transmission line, respectively,

each of the first ground conductors having a first ground conductorportion 20 a extending along the first high-frequency transmission lineportion 19 a and second ground conductor portions 20 b, 20 c extendingfrom both longitudinal ends of the first ground conductor portion alongthe second high-frequency transmission line portions 19 b, 19 c,respectively;

d) a second dielectric substrate 16 for hermetic sealing, overlaid onthe one surface of the first dielectric substrate so as to cover thefirst high-frequency transmission line portion and the first groundconductor portions; and

e) a second ground conductor 17 formed on the other surface of the firstdielectric substrate over an region including the high-frequencytransmission line 19, the first ground conductors 20, and gaps havingwidths g1 to g4 between the high-frequency transmission line and thefirst ground conductors, in a thickness direction of the firstdielectric substrate,

the second ground conductor constituting first line means 38 togetherwith the first high-frequency transmission line portion, the firstground conductor portions and the first and second dielectric substratesand constituting second line means 39, 40 together with the secondhigh-frequency transmission line portion, the second ground conductorportions and the first dielectric substrate,

wherein a first width W19 a of the first high-frequency transmissionline portion is smaller than a second width W19 of the secondhigh-frequency transmission line portion (W19 a<W19),

a first distance G1 between the first ground conductor portions 20 a onboth sides of the first high-frequency transmission line portion 19 a inthe width direction of the first ground conductor portions 20 a is equalto or smaller than a second distance G2 between the second groundconductor portions 20 b or 20 c on both sides of the secondhigh-frequency transmission line portion 19 b, 19 c (G1≦G2) in the widthdirection of the first ground conductor portions 20 b, 20 c and

a thickness d16 of the second dielectric substrate is selected to belarger than a thickness d15 of the first dielectric substrate (d16>d15),and the first width W19 a and the regions g1, g2 between the firsthigh-frequency transmission line portion and the first ground conductorportions are selected so that a characteristic impedance Z19 a of thefirst line means is smaller than a characteristic impedance 19 of thesecond line means (Z19 a<Z19), in order to make approximation of atransmission mode of the first line means to a transmission mode of thesecond line means.

In a second aspect of the invention, the first width W19 a and firstgaps g1, g2 are selected so that the a ratio Z19 a/Z19 of thecharacteristic impedance Z19 a of the first line means to thecharacteristic impedance 19 of the second line means meets the followingrelationship:

0.5≦Z19 a/Z19≦0.9

In a third aspect of the invention, a high-frequency input/outputfeedthrough comprises:

a first dielectric substrate having one surface where a line conductorand cofacial ground layers spaced at a same distance from both sides ofthe line conductor uniformly in a longitudinal direction of the lineconductor are formed, the other surface where a bottom face ground layeris formed, and side faces where side ground layers are formed; and

a second dielectric substrate joined to the one surface of the firstdielectric substrate so as to sandwich portions of the line conductorand the cofacial ground layers between the first and second substrates,

wherein the second dielectric substrate is made thicker than the firstdielectric substrate,

the portion of the line conductor sandwiched between the first andsecond substrates is made narrower than the other portions thereof inwidth, and

the portions of the cofacial ground layers sandwiched between the firstand second substrates project toward the line conductor uniformly in alongitudinal direction of the line conductor so as to be spaced at asame distance from both sides of the line conductor.

In a fourth aspect of the invention, the first dielectric substrate hasa dielectric constant ∈_(r)15 and a thickness d15, and a thickness d16of the second dielectric substrate having a dielectric constant ∈_(r)16is ∈_(r)15/(2∈_(r)16) or more times the thickness d15 of the firstdielectric substrate.

In a fifth aspect of the invention, the thickness d16 of the seconddielectric substrate is ∈_(r)15/∈_(r)16 or more times the thickness d15of the first dielectric substrate.

In a sixth aspect of the invention, heights h1, h2 of the projectionstoward the line conductor of the portions of the cofacial ground layerssandwiched between the first and second dielectric substrates or thegaps g1, g2 between the line conductor and the cofacial ground layersare ∈_(r)15/(2∈_(r)16) or less times the thickness d15 of the firstdielectric substrate.

In a seventh aspect of the invention, the dielectric constant ∈_(r)15 ofthe first dielectric substrate is smaller than the dielectric constant∈_(r)16 of the second dielectric substrate.

In an eighth aspect of the invention, an upper ground layer is providedon a surface of the second dielectric substrate of an opposite side tothe first dielectric substrate, and side ground layers are provided onside faces of the second dielectric substrate.

In a ninth aspect of the invention, the first and second dielectricsubstrates are made of one or more materials selected from a group ofmaterials including alumina, mullite, glass ceramics,polytetrafluoroethylene (PTFE), glass epoxy resins and polyimides.

In a tenth aspect of the invention, the line conductor and the cofacialground layers are made of one or more materials selected from a group ofmaterials including Cu, MoMn+Ni+Au, W+Ni+Au, Cr+Cu, Cr+Cu+Ni+Au,Ta₂N+NiCr+Au, Ti+Pd+Au, and NiCr+Pd+Au.

In an eleventh aspect of the invention, a package for housing ahigh-frequency semiconductor element comprises:

a substrate made of a dielectric or metal, having one surface includinga mounting portion on which the high-frequency semiconductor element ismounted;

a frame made of a dielectric or metal, joined to the substrate so as toenclose the mounting portion, the frame being notched to form aninput/output feedthrough mounting portion whose side faces and bottomface are electrically conductive;

the high-frequency input/output feedthrough of any one of theabove-mentioned constructions, fitted to the input/output feedthroughmounting portion; and

a cap attached to a top face of the frame.

In a twelfth aspect of the invention, a package for housing ahigh-frequency semiconductor element comprises:

a dielectric substrate having one surface including a mounting portionon which the high-frequency semiconductor element is mounted;

a line conductor formed from a proximity of the mounting portion to aproximity of a periphery of the dielectric substrate on the one surfaceof the dielectric substrate;

first ground layers arranged from a proximity of the mounting portion toa proximity of a periphery of the dielectric substrate on the onesurface of the dielectric substrate so as to be spaced at a samedistance from both sides of the line conductor;

a dielectric frame joined to the one surface of the dielectric substrateso that the mounting portion is enclosed by the dielectric frame andportions of the line conductor and the first ground layers aresandwiched between the dielectric substrate and the dielectric frame;

a second ground layer formed on the other surface of the dielectricsubstrate; and

a connecting conductor layer for connecting the second ground layer tothe first ground layers,

wherein the dielectric frame is made thicker than the dielectricsubstrate,

the portion of the line conductor sandwiched between the dielectricsubstrate and the dielectric frame is made narrower than the otherportions thereof in width, and

the portions of the first ground layers sandwiched between thedielectric substrate and the dielectric frame project toward the lineconductor uniformly in a longitudinal direction of the line conductor soas to be spaced at a same distance from both sides of the lineconductor.

In a thirteenth aspect of the invention, the dielectric substrate has adielectric constant ∈_(r)15 and a thickness d15, and a thickness d16 ofthe dielectric frame having a dielectric constant ∈_(r)16 is∈_(r)15/(2∈_(r)16) or more times the thickness d15 of the dielectricsubstrate.

In a fourteenth aspect of the invention, the thickness d16 of thedielectric frame is ∈_(r)15/(∈_(r)16) or more times the thickness d15 ofthe dielectric substrate.

In a fifteenth aspect of the invention, heights h1, h2 of theprojections toward the line conductor of the portions of the firstground layers sandwiched between the dielectric substrate and thedielectric frame or the gaps g1, g2 between the line conductor and thefirst ground layers are ∈_(r)15/(2∈_(r)16) or less times the thicknessd15 of the first dielectric substrate.

In a sixteenth aspect of the invention, the dielectric constant ∈_(r)15of the dielectric substrate is smaller than the dielectric constant∈_(r)16 of the dielectric frame.

In a seventeenth aspect of the invention, an upper ground layer isprovided on a surface of the dielectric frame of an opposite side to thedielectric substrate, and side ground layers are provided in an interiorof the dielectric frame above the connecting conductor layer.

In an eighteenth aspect of the invention, the dielectric substrate andthe dielectric frame are made of one or more materials selected from agroup of materials including alumina, mullite, glass ceramics,polytetrafluoroethylene (PTFE), glass epoxy resins and polyimides.

In a nineteenth aspect of the invention, the line conductor and thefirst ground layers are made of one or more materials selected from agroup of materials including Cu, MoMn+Ni+Au, W+Ni+Au, Cr+Cu,Cr+Cu+Ni+Au, Ta₂N+NiCr+Au, Ti+Pd+Au, and NiCr+Pd+Au.

In a twentieth aspect of the invention, a high-frequency semiconductorapparatus comprises:

a semiconductor element installed in a space on the dielectric substrateof the package for housing a high-frequency semiconductor element of anyone of the above-mentioned constructions, enclosed by the frame, thesemiconductor element being electrically connected to the input/outputfeedthrough for high-frequency.

According to the high-frequency input/output feedthrough of theinvention, the width w19 a of the portion 19 a of the line conductor 19which is sandwiched between the lower dielectric substrate 15 and theupper dielectric substrate 16 is smaller than the width w19 of the otherportions 19 b, 19 c, and the portions 20 a 1 of the cofacial groundlayers disposed on both sides of the line conductor to be spaced at thesame distance from both sides of the line conductor are projected towardthe portion 19 a of the line conductor 19 by the heights h1, h2,respectively, so that gaps g1, g2 (g1=g2)are preserved. Therefore, theelectric field distribution in the portion in which the line conductoris sandwiched between the lower dielectric substrate and the upperdielectric substrate and which corresponds to the stripline becomessimilar to the electric field distributions in the other portions whichare in front and in rear of the portion, in which the line conductor isexposed, and which correspond to the microstrip line. This causes thetransmission modes for a high-frequency signal in the two kinds ofportions to become similar to each other. Even when the characteristicimpedances of the two kinds of portions are different from each other,therefore, return and insertion losses due to a difference of thetransmission modes are not produced. As a result, excellent transmissioncharacteristics for a high-frequency signal can be obtained.

According to the package for housing a high-frequency semiconductorelement of the invention, the high-frequency input/output feedthroughpart is structured by using the above-mentioned high-frequencyinput/output feedthrough of the invention. In a transmission of ahigh-frequency signal between a high-frequency semiconductor elementhoused in the package and an external electric circuit, therefore,return and insertion losses due to a difference of the transmissionmodes in the input/output feedthrough are not produced. Consequently, apackage for housing a high-frequency semiconductor element which hasexcellent transmission characteristics for a high-frequency signal andwhich has superior high-frequency characteristics can be obtained.

As a result, According to the invention, it is possible to provide ahigh-frequency input/output feedthrough in which the transmission modesfor a high-frequency signal in a line conductor are matched with eachother, thereby reducing the return and insertion losses, and which hasexcellent transmission characteristics.

According to the invention, it is possible to provide a package forhousing a high-frequency semiconductor element in which the transmissionmodes for a high-frequency signal in a line conductor of an input/outputfeedthrough part are matched with each other, thereby reducing thereturn and insertion losses, and which has excellent transmissioncharacteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

Other and further objects, features, and advantages of the inventionwill be more explicit from the following detailed description taken withreference to the drawings wherein:

FIG. 1A is a plane view showing a high-frequency input/outputfeedthrough of an embodiment of the invention, FIG. 1B is a sectionalview taken along line III—III of FIG. 1A, and FIG. 1C is a sectionalview taken along line IV—IV of FIG. 1A;

FIGS. 2A and 2B are sectional views taken along lines III—III and V—V ofFIG. 1A, illustrating the electric field distribution of thehigh-frequency input/output feedthrough of the invention;

FIG. 3 is a partially cutaway perspective view showing a package forhousing a high-frequency semiconductor element of an embodiment of theinvention;

FIG. 4 is a partially cutaway perspective view showing a package forhousing a high-frequency semiconductor element of another embodiment ofthe invention;

FIG. 5 is a diagram showing frequency characteristics of return loss ina high-frequency input/output feedthrough;

FIG. 6 is a diagram showing frequency characteristics of insertion lossin a high-frequency input/output feedthrough;

FIG. 7 is a schematic plane view showing part of the high-frequencyinput/output feedthrough as shown in FIGS. 1 and 2;

FIG. 8 is a diagram showing the relationship between characteristicimpedance ratio and reflection coefficient Γ of line means 38, 39, 49representing the inventor's experiment results;

FIG. 9 is a front view showing part of another embodiment of theinvention;

FIG. 10 is a sectional view showing part of another embodiment of theinvention;

FIG. 11 is a sectional view showing part of still another embodiment ofthe invention;

FIG. 12 is a perspective view showing an input/output feedthrough 24 ofanother embodiment of the invention;

FIG. 13 is a plane view showing part of the embodiment shown in FIG. 12;

FIG. 14 is a perspective view showing an input/output feedthrough 65 ofanother embodiment of the invention;

FIG. 15 is a simplified plane view showing the input/output feedthrough65 shown in FIG. 14;

FIGS. 16A and 16B are sectional views showing electric fielddistribution of the input/output feedthrough 65;

FIG. 17 is an exploded perspective view showing a semiconductorapparatus provided with the input/output feedthrough 65 shown in FIGS.14 and 15;

FIG. 18 is a sectional view of the semiconductor apparatus of FIG. 17;

FIG. 19A is a plane view showing an example of a prior arthigh-frequency input/output feedthrough and FIG. 19B is a sectional viewtaken along line I—I of FIG. 19A; and

FIG. 20A is a plane view showing another example of a prior arthigh-frequency input/output feedthrough and FIG. 20B is a sectional viewtaken along line II—II of FIG. 20A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now referring to the drawings, preferred embodiments of the inventionare described below.

Hereinafter, the invention will be described with reference to theaccompanying drawings. The invention is not restricted to embodimentsdescribed below, and various changes and modifications may be made inthe invention without departing from the scope thereof.

In the drawings, parts except sectional parts are hatched by continuousor broken lines for ready appreciation. An input/output feedthrough ofthe invention is used in a high-frequency range, namely a range of 30 to300 GHz, preferably a range of 40 to 70 GHz.

FIG. 1 shows an embodiment of the high-frequency input/outputfeedthrough of the invention. FIG. 1A is a plane view, and FIG. 1B is asectional view taken along line III—III of FIG. 1A, and FIG. 1C is asectional view taken along line IV—IV of FIG. 1A.

FIGS. 2A and 2B are sectional views taken along lines III—III and V—V ofFIG. 1A, illustrating the electric field distribution of thehigh-frequency input/output feedthrough of FIG. 1.

In these figures, a lower dielectric substrate 15 and an upperdielectric substrate 16 are used also as a hermetically sealing part ina signal input/output feedthrough part of a package for housing ahigh-frequency circuit. A bottom face ground layer 17 is formed on theentire bottom face of the lower dielectric substrate 15, side faceground layers 18 are formed on the side faces, and a line conductor 19and cofacial ground layers 20 which are disposed on both sides of theline conductor 19 in the longitudinal direction thereof (left-rightdirection in FIG. 1A) to be separated from the line conductor 19 at thesame distance (namely, g1=g2, g3=g4) are formed on the top face of thelower dielectric substrate 15. The bottom face ground layer 17, the sideface ground layers 18, and the cofacial ground layers 20 are connectedto each other to form a ground face of the same potential. The side faceground layers 18 are composed of ground layers 18 a formed on the lowerdielectric substrate 15 and ground layers 18 b formed on the upperdielectric substrate 16.

The upper dielectric substrate 16 is joined onto the lower dielectricsubstrate 15 so as to sandwich portions of the line conductor 19 and thecofacial ground layers 20. A thickness d16 of the upper dielectricsubstrate 16 is made larger than a thickness d15 of the lower dielectricsubstrate 15 (d16>d15). A width W19 a of the portion 19 a of the lineconductor 19 sandwiched between the lower dielectric substrate 15 andthe upper dielectric substrate 16 is made smaller than a width W19 ofthe other portions 19 b, 19 c, i.e., the portions which are in front andin rear of the portion and in which the line conductor 19 is exposed,thereby forming a narrow portion 19 a (W19 a<W19). Each of the cofacialground layers has a projected portion 20 a 1 having a projection heighth1, h2 in the thickness direction of the cofacial ground layers towardthe narrow portion 19 a of the line conductor 19 so as to extenduniformly in the longitudinal direction thereof spaced at the distanceg1, g2 (g1=g2) from both sides of the line conductor.

According to the configuration of the high-frequency input/outputfeedthrough of the prior art as shown in FIG. 20, in line means 71sandwiched between a lower dielectric substrate 7 of the line conductor9 and an upper dielectric substrate 8, the thickness of the lowerdielectric substrate 7 is nearly equal to that of the upper dielectricsubstrate 8 (d7=d8), and cofacial ground layers 12 are disposed on bothsides of the line conductor 9. However, since such projected portion 20a of the present invention is not provided, the distances g11, g12between the line conductor 9 and the cofacial ground layers 12 arelonger (g11=g12>g13=g14), and additionally since an top face groundlayer 11 is formed on the top face of the upper dielectric substrate 8and side ground layers are formed on the side faces thereof, an electricfield on the upper dielectric substrate 8 side distributes toward thetop face ground layer in a substantially identical form with that of thelower dielectric substrate 7 side, which is similar to socalled TEM(transverse electromagnetic) mode.

On the other hand, in the line means 72, 73 which are in front and inrear of the above-mentioned portion, since air exists above the lineconductor 9, the electric field in the lower dielectric substrate isdistributed with being mainly directed to the lower and side face groundlayers. Namely, the electric field distribution is of the quasi-TEMmode. Therefore, the TEM mode of the line means 71 and the quasi-TEMmode of the line means 72, 73 are different in transmission mode forhigh-frequency signals, whereby return and insertion losses are caused.

By contrast, according to the high-frequency input/output feedthrough ofthe invention, whose electric field distribution is shown by arrows inFIGS. 2A, 2B, as shown in FIG. 2A which is a sectional view taken alongline III—III, a line conductor portion 19 a of the line conductor 19 ismade to have a narrow line width W19 a so that the characteristicimpedance Z19 a of the line means 38 is different from but closelyanalogous to the characteristic impedance Z19 of the line means 39, 40(W19 a<W19).

To correspond to the line conductor portion 19 a of the line conductor19, the thickness d16 of the upper dielectric substrate 16 is madelarger than the thickness d15 of the lower dielectric substrate 15, andin addition the cofacial ground layers are provided with the projectedportions 20 a 1 which are spaced at the same distance from both sides ofthe line conductor (g1=g2), to avoid the distances g1, g2 from exceedingthe distances g3, g4. Accordingly , the electric field is concentratedon the lower dielectric substrate 15 side toward the bottom face groundlayer 17 and the cofacial ground layers 20, and on the upper dielectricsubstrate 16 side, the electric field distribution as shown by arrows ofbroken line in FIG. 2A can be substantially eliminated , so that theelectric field distribution of the line means 38 can be shaped into theform of quasi-TEM mode, and can be made closely analogous to thequasi-TEM mode of electric distribution as shown in FIG. 2B which is asectional view taken along line V—V. As a result, the transmission modefor high-frequency signals of the line conductor portion 19 a can bemade closely analogous to that of the line conductor portions 19 b, 19c, and although a difference occurs between the characteristic impedanceZ19 a of the line means 38 including the line conductor portion 19 asandwiched between the lower dielectric substrate 15 and the upperdielectric substrate 16 and the characteristic impedance Z19 of the linemeans 39, 40 including the line conductor portions 19 b, 19 c, returnand insertion losses due to the difference in transmission mode can bereduced, with the result that the input/output feedthrough has excellenttransmission characteristics.

The first distance G1 between the first ground conductor portions 20 ain the width direction thereof on both sides of the first high-frequencytransmission line portion 19 a is equal to or smaller than the seconddistance G2 between the second ground conductor portions 20 b; 20 c inthe width direction thereof on both sides of the second high-frequencytransmission line portion 19 b; 19 c (G1≦G2).

In the embodiment, although the input/output feedthrough is configuredsymmetrical about a plane perpendicular to a paper sheet of FIG. 1Aincluding line IV—IV of FIG. 1, the input/output feedthrough may beconfigured asymmetrical, that is g1≠g2 and g3≠g4.

The lower and upper dielectric substrates 15, 16 are made of one or morematerials selected from a group of materials including, for example, aceramic material such as alumina or mullite, so-called glass ceramics(glass and ceramics), or a resin material such as Teflon (PTFE), glassepoxy, or polyimide.

The thickness and width of each of the dielectrics are set in accordancewith the frequency of the high-frequency signal to be transmitted, thecharacteristic impedance, etc. In the invention, it is important to makethe thickness d16 of the upper dielectric substrate 16 larger than thethickness d15 of the lower dielectric substrate 15. Preferably, thethickness d16 of the upper dielectric substrate 16 in the narrow portion19 a of the line conductor 19 is ∈_(r)15/∈_(r)16^(½) or more times thethickness d15 of the lower dielectric substrate 15. $\begin{matrix}{{d16} \geqq {{d15} \cdot \frac{ɛ_{r}15}{\sqrt{ɛ_{r}16}}}} & (1)\end{matrix}$

In this case, the electric field distribution in a plane perpendicularto the transmission direction in the narrow portion 19 a of the lineconductor 19 is concentrated in a more conspicuous manner toward thebottom face ground layer 17 side and the side face ground layers 18side, so that the transmission mode (refer to FIG. 2B) can be madesimilar to that of the line conductor portions 19 b, 19 c of the lineconductor 19 in front and rear of the narrow portion 19 a. Therefore,the transmission characteristics for high-frequency signals are furtherimproved.

By contrast, when the thickness d16 of the upper dielectric substrate 16is less than ∈_(r)15/(2×∈_(r)16^(½)) times the thickness d15 of thelower dielectric substrate 15, it seems from results of the inventor'sactual measurement that that adversely affects the degree ofelectromagnetic coupling. Therefore, it is preferable to set thethickness d16 of the upper dielectric substrate 16 to be∈_(r)15/(2×∈_(r)16^(½)) or more times the thickness d15 of the lowerdielectric substrate 15. By satisfying the following relation, thetransmission mode of the second line means (refer to FIG. 2A) is madesimilar to the transmission mode of the second line means 39, 40 (referto FIG. 2B), with the result that the input/output feedthrough of theinvention is realized in which the return of electromagnetic waves isreduced. $\begin{matrix}{{d16} \geqq {{d15} \cdot \frac{ɛ_{r}15}{2\sqrt{ɛ_{r}16}}}} & (2)\end{matrix}$

For example, when alumina (∈_(r)=9) is used as the dielectric material,∈_(r)15/(2×∈_(r)16^(½))=1.5. Consequently, it is preferable to set thethickness d16 of the upper dielectric substrate 16 to be 1.5 or moretimes the thickness d15 that of the lower dielectric substrate 15.

The upper dielectric substrate 16 may be made of the same material asthat of the lower dielectric substrate 15. Alternatively, when thedielectric constant ∈ 16 of the upper dielectric substrate 16 is madesmaller than ∈ 15 of the lower dielectric substrate 15 (∈16<∈15), theabove-mentioned effects are attained more remarkably, and therefore thisconfiguration is preferable. According to this configuration, even whenthe distances g1, g2 between the projected portions 20 a 1 and thenarrow portion 19 a are made larger, namely, the projection heights h1,h2 are made smaller, or h1=0 and h2=0, the return of electromagneticwaves can be reduced to make the transmission modes of the line means38; 39, 40 analogous to each other.

The line conductor 19 and the cofacial ground layers 20 are made of ametal material for the high-frequency line conductor, such as Cu,MoMn+Ni+Au (these metals are laminated in this order from below to aboveon the lower dielectric substrate 15, and hereinafter described in thesame manner), W+Ni+Au, Cr+Cu, Cr+Cu+Ni+Au, Ta₂N+NiCr+Au, Ti+Pd+Au, orNiCr+Pd+Au, by using a thick film printing method, various thin filmforming methods, or a plate processing method. The thicknesses andwidths of the components are set in accordance with the frequency of thehigh-frequency signal to be transmitted and an ideal characteristicimpedance.

When the width W19 a of the line conductor 19 in the line means wherethe upper dielectric substrate 16 is joined to the lower dielectricsubstrate 15 is made smaller than the width W19 of the other portions 19b, 19 c of the line conductor 19, the widths W19 a, W19 are suitably setin the range from the width W19 a corresponding to the idealcharacteristic impedance to the line width w19 in the other portions inaccordance with the required specifications, namely, so that the lineconductor 19 is tapered in the longitudinal direction thereof (left toright direction of FIG. 1A) from the boundaries 41, 42 between theportion 19 a and the portions 19 b, 19 c to the portion 19 a of therequired width W19 a (left to right direction of FIG. 1A), in order toreduce the electromagnetic return. Alternately the width of the lineconductor may be reduced stepwise from the boundaries to the lineconductor portions 19 a of the required width W19 a or any other formmay be appropriately employed.

In the embodiment of the invention, the line means 38 where the upperdielectric substrate 16 is disposed is configured in such a manner thatthe end faces 43, 44 of the line conductor 19 in the upper dielectricsubstrate 16 exist within the ranges of the tapered boundaries 41, 42,respectively. Thereby, even when the arranged position of the upperdielectric substrate 16 is slightly displaced in the longitudinaldirection of the line conductor 19, the stripline 38 has a predeterminedcharacteristic impedance Z19 a and the transmission mode is keptunoiform, when the end faces 43, 44 exist within the ranges of thetapered boundaries 41, 42, repectively.

The intervals g3, g4 between the line conductor 19 and the cofacialground layers 20 may be usually set to be standard values which areapplied in obtaining a desired characteristic impedance by providing thecofacial ground layers 20. In the case where each of the cofacial groundlayers 20 is projected toward the portion 19 a of the line conductor 19by the amounts of projection h1, h2 so as to be disposed at the sameintervals (g1=g2, g3=g4) in the first line means 38 which is the jointportion between the upper dielectric substrate 16 and the lowerdielectric substrate 15, the amounts of projection h1, h2 or theintervals g1, g2 between the ground layers and the line conductor 19 ais adequately set to be ∈_(r)15/(2 (∈_(r)16))^(½) or less times thethickness of the lower dielectric substrate 15, in accordance withrequired characteristics and in consideration of the degree of theabove-mentioned effect on the electromagnetic field.

The bottom face ground layer 17 and side face ground layers 18 areformed so as to cover the almost whole of the lower and side faces ofthe lower dielectric substrate 15 by using the same material as the lineconductor 19 and the cofacial ground layers 20, and in the same manner.For example, the thicknesses of the layers are set to be about 20 μm inthe case of a thick film, and about 5 μm in the case of a thin film.

In the high-frequency input/output feedthrough of the invention, anupper-face ground layer 75 and side face ground layers 18 b may befurther disposed on the upper and side faces of the upper dielectricsubstrate 16. When such layers 75, 18 b are disposed, the transmissionmodes in line means 38 and line means 39, 40 are matched by thefunctions of the thicknesses d15, d16 of the lower and upper dielectricsubstrates 15 and 16 and the projected portions 20 a 1 of the cofacialground layers 20, so that return and insertion losses can be reduced.Furthermore, this configuration causes the line conductor 19 a to besurrounded by the ground layers 20, 18 a, 18 b, 17, 75, so as tofunction as a shield against a high-frequency signal.

The bottom face ground layer 17, the side face ground layers 18, or theupper-face layer 18 b and side face ground layer 75 of the upperdielectric substrate 16 may be formed as a metal film layer.Alternatively, these layers may be formed by attaching a metal plate ora metal block.

Referring to FIG. 8, the result of an experiment carried out by theinventor of the present invention will be described. This experimentalresult has a constitution described in a later-mentioned firstembodiment. It is so constituted that the characteristic impedance Z19of the line means 39, 40 becomes 50 Ω. The width W19 a of the lineconductor 19 and the intervals g1, g2 are varied in the later-mentionedembodiment 1 so that the transmission mode of the line means 38coincides with the transmission modes of the line means 39, 40, and thecharacteristic impedance Z19 a of the line means 38 is determined, andthen relationships between a ratio η(=Z19 a/Z19) of the characteristicimpedances Z19 a and Z19, and a reflection coefficient Γ of thetransmission signal viewed from the line means 39 toward the line means38, thereby obtaining a characteristics denoted by a concrete line inFIG. 8. This proved that a ratio η(=Z19 a/Z19) of the characteristicimpedances at which the reflection coefficient Γ becomes below 0.44 isbetween 0.5 and 0.9.

0.5≦Z19a/Z19≦0.9  (3)

Therefore, it can be understood that by selecting the thickness d16 ofthe dielectric substrate 16 to be larger than the thickness d15 of thedielectric substrate 15 (d16>d15) and selecting the width W19 a and theintervals g1, g2 so that the characteristic impedance Z19 a of the linemeans 38 becomes below the characteristic impedance Z19 of the linemeans 39, 40, it is possible to approximate the transmission mode of theline means 38 to the transmission mode of the line means 39, 40. Morepreferably, the ratio η of the characteristic impedances preferablysatisfies the equation (3) as described above.

As is apparent from FIG. 8, a good property can be obtained at thecharacteristic impedance ratio η of 0.7 at which the reflectioncoefficient Γ minimum. The characteristic impedance Z19 of the linemeans 39, 40 is 50 Ω, and the characteristic impedance Z19 a of the linemeans 38 is 35 Ω. This experimental result of FIG. 8 represents acharacteristics in a constitution including jigs used in a measurement.The broken line in FIG. 8 represents the characteristics of theconventional high-frequency input/output feedthrough shown in FIG. 20.For the experimental result of the present invention denoted by theconcrete line in FIG. 8, frequency of the electromagnetic wave is withinthe range from 40 to 70 GHz. For the characteristics in the constitutionof FIG. 20 which is denoted by the broken line in FIG. 8, frequency ofthe electromagnetic wave is within the range from 0.45 to 40 GHz.

Next, the package for housing a high-frequency semiconductor element ofthe invention will be described with reference to the accompanyingdrawings.

FIG. 3 is a partially cutaway perspective view showing an embodiment ofthe package for housing a high-frequency semiconductor element of theinvention.

In FIG. 3, a substrate 21 is made of a dielectric material, a metal orthe like. A mounting portion 21 a for mounting a high-frequencysemiconductor element 63 is formed on the upper face of the substrate.In the embodiment, the mounting portion 21 a is formed into a recessedshape. Alternatively, the portion may be formed as a flat face on thesubstrate 21. A frame 22 is joined onto the substrate 21 so as tosurround the mounting portion 21 a, and is made of a dielectric, ametal, or the like in the same manner as the substrate 21. Aninput/output feedthrough attaching portions 23 are formed by cuttingaway the frame 22, and in which side faces 45, 46 and bottom face 47thereof are electrically conductive. In the embodiment, similar cutawayportions are formed also in the substrate 21 so as to constitute theinput/output feedthrough attaching portions 23. In the case where thesubstrate 21 and the frame 22 are made of a metal, the side faces 45, 46and the bottom face 47 of the input/output feedthrough attachingportions 23 are naturally conductive. In the case where the substrate 21and the frame 22 are made of a dielectric, a conductor layer is formedso as to cover the faces, thereby making the faces conductive. The sidefaces 45, 46 and the bottom face 47 are grounded via the substrate 21and the frame 22 or a ground conductor layer (not shown) formed so as tocover the substrates and the frame.

High-frequency input/output feedthroughs 24 of the invention configuredas described above are fitted into the input/output feedthroughattaching portions 23. A lower dielectric substrate 25, an upperdielectric substrate 26, a bottom face ground layer 27 which is formedon the bottom face of the lower dielectric substrate 25, side faceground layers 28 which are formed on the side faces, a line conductor 29which is formed on the upper face of the lower dielectric substrate 25,and cofacial ground layers 30 which are disposed on both the sides ofthe line conductor 29 with being separated from the line conductor bythe same interval. The lower dielectric substrate 25 corresponds to thelower dielectric substrate 15 as shown in FIGS. 1 and 2, the upperdielectric substrate 26 corresponding to the upper dielectric substrate16 as shown in FIGS. 1 and 2. The bottom face ground layer 27, the sideface ground layers 28, and the cofacial ground layers 30 are connectedto each other to form a ground face of the same potential. The upperdielectric substrate 26 is joined onto the lower dielectric substrate 25with sandwiching a portion of the line conductor 29 and a portion ofeach of the cofacial ground layers 30. A thickness d26 of the upperdielectric substrate 26 is made thicker than a thickness d25 of thelower dielectric substrate 25. The width of the portion 29 a of the lineconductor 29 which is sandwiched between the lower dielectric substrate25 and the upper dielectric substrate 26 is made smaller than that ofthe other portions 29 b, 29 c (i.e. the portions which are in front andin rear of the upper dielectric substrate 26 and in which the lineconductor 29 is exposed), thereby forming a narrow portion 29 a.Projected portions 30 a like the above described projected portions 20 a1 are disposed in the portions of the cofacial ground layers 30 whichportions are sandwiched between the lower dielectric substrate 25 andthe upper dielectric substrate 26. The projected portions 30 a areprojected toward the narrow portion 29 a of the line conductor 29 withforming the same interval. The bottom face ground layer 27 and the sideface ground layers 28 are electrically connected to the conductive sidefaces 45, 46 and bottom face 47 of the input/output feedthroughattaching portions 23 to be grounded, respectively.

According to the package for housing a high-frequency semiconductorelement of the invention, the high-frequency input/output feedthroughparts are structured by using the high-frequency input/outputfeedthroughs 24 of the invention which are configured as describedabove. In a transmission of a high-frequency signal between ahigh-frequency semiconductor element housed in the package and anexternal electric circuit, therefore, return and insertion losses due toa difference of the transmission modes in the high-frequencyinput/output feedthroughs 24 are not produced as described above.Consequently, a package for housing a high-frequency semiconductorelement which is of the so-called metal wall type (in the case havingthe metal frame 22), which has excellent transmission characteristicsfor a high-frequency signal, and which has superior high-frequencycharacteristics can be obtained.

Terminal electrodes of the high-frequency semiconductor element mountedon the mounting portion 21 a, and wiring conductors of external circuitsare connected to the line conductors 29 via wires or ribbons so that thehigh-frequency semiconductor element in the package is electricallyconnected to the external circuits. A cover 50 which is made of an Fe—Nialloy such as Fe—Ni—Co, or Fe—Ni 42 alloy, oxygen free copper, aluminum,stainless steel, a Cu—W alloy, a Cu—Mo alloy, or the like is attached tothe upper face of the frame 22 by soldering, high-melting metal soldersuch as AuSn solder, or AuGe solder, seam welding, or the like. As aresult, the high-frequency semiconductor element is housed in thepackage in a hermetically sealed manner, thereby constituting ahigh-frequency semiconductor device as a product.

In accordance with the specifications of the package, the substrate 21and the frame 22 are made of the same dielectric as that of thehigh-frequency input/output feedthroughs 24, and thus in the where thesecomponents are made of a dielectric, at least the side faces 45, 46 andbottom face 47 of the input/output feedthrough attaching portions 23 aremade electrically conductive. In other embodiment, the substrate 21 maybe made of the same metal as that of the metal frame 22.

The substrate 21 and the frame 22 are joined together by one of thehigh-melting metal solders among AgCu solder, AuSn solder, and AuGesolder. The high-frequency input/output feedthroughs 24 are fitted intothe input/output feedthrough attaching portions 23 and joined thereto bysimilar high-melting metal solder.

In the embodiment, the upper face of the upper dielectric substrate 26is cofacial with that of the frame 22. According to this configuration,the cover 50 which is made of metal or dielectric may be attached tothese upper faces directly or via a frame-like metal seal or the like,thereby enabling the high-frequency semiconductor element mounted on themounting portion 21 a to be easily housed in the package in ahermetically sealed manner. Furthermore, in the case where the upperface 25 a of the upper dielectric substrate 26 is not cofacial with theupper face 22 a of the frame 22 as shown in FIG. 9 in other embodiment,a cover 50 having a projection 49 which is shaped so as to eliminate thestep between the upper faces is used or the attachment is conducted viaa metal seal, so that the high-frequency semiconductor element can besimilarly housed in the package in a hermetically sealed manner.

In the embodiment of FIG. 3, one high-frequency input/output feedthrough24 is disposed in each of the sides of the substrate 21. Alternatively,the input/output feedthroughs may be disposed at other positions, orplural input/output feedthroughs may be disposed in one side (3 in FIGS.10, 2 in FIG. 11) as shown in FIGS. 10 and 11. In such an alternative,plural input/output feedthrough attaching portions 23 are disposed andplural high-frequency input/output feedthroughs 24 are attached in aparallel manner. In FIGS. 10 and 11, the substrate 21 and the frame 22may be made of dielectric. In the constitution of FIG. 10, on both rightand left side faces of the input/output feedthroughs 24, groundedconductive layers 52 to 55 are formed and electrically and hermeticallyconnected using the solders or the like. In the embodiment of FIG. 11,on both side faces of each input/output feedthrough 24, conductivelayers 56 to 59 which are grounded, are formed and electricallyconnected using the solders as described above.

In still another embodiment, the substrate 21 and the frame 22 are madeof metal. In this constitution, at both side faces 53, 54 of theadjacent input/output feedthroughs 24, grounded conductive layers aredisposed and the other conductive layers 52 and 55 may be omitted. Inthe embodiment of FIG. 11, the conductive layers 56 to 59 are omitted,and a conductive interface 60 is disposed between the input/outputfeedthroughs 24 so as to be electrically connected with the substrate21. Other constitutions in FIGS. 9 to 11 are similar to those of theabove described embodiment.

In the package for housing a high-frequency semiconductor element of theinvention shown in FIG. 3 also, an upper-face ground layer 75 and side face ground layers 18 b similar to those in FIG. 1 may be furtherdisposed on the upper and side faces of the upper dielectric substrate26 of each of the high-frequency input/output feedthroughs 24. When suchlayers 75; 18 b are disposed, the transmission modes are matched by thefunctions of the thicknesses d25, d26 of the lower and upper dielectricsubstrates 25 and 26 and the projected portions 30 a of the cofacialground layers 30, so that return and insertion losses can be reduced.Furthermore, this configuration causes the line conductor 29 a to besurrounded by the ground layers, so as to function as a shield against ahigh-frequency signal.

The bottom face ground layer 27, the side face ground layers 28, and theside face ground layers 18 b and upper-face ground layer 75 of the upperdielectric substrate 26 (cf. FIG. 1) may be formed as a metal filmlayer. Alternatively, in the input/output feedthroughs 24 shown in FIG.12, for electrically connecting the cofacial ground layer 30 with theupper-face ground layer of the upper dielectric substrate 26, the layersmay be configured as a substantially continuous ground layer byarranging a number of through conductors 61, 62 in the upper dielectriclayer 26 as shown in FIG. 12 or connecting the conductors, so as tofunction in the same manner as a film layer, or by attaching a metalplate or a metal block. FIG. 13 is a simplified plane view showing theembodiment in FIG. 12.

FIG. 4 is a partially cutaway perspective view showing anotherembodiment of the package for housing a high-frequency semiconductorelement of the invention.

Referring to FIG. 4, a dielectric substrate 31 is made of the samematerial as that of the above-mentioned lower dielectric substrate 15 orupper dielectric substrate 16. A mounting portion 31 a for mounting ahigh-frequency semiconductor element 63 is formed in the upper face ofthe substrate. In the embodiment, the mounting portion 31 a is formedinto a flat face. Alternatively, the portion may be formed as a recessedshape. A line conductor 32 is formed on the upper face of the dielectricsubstrate 31 so as to elongate from the vicinity of the mounting portion31 a to the vicinity of the outer periphery of the dielectric substrate31. Cofacial ground layers 33 are disposed on both the sides of the lineconductor 32 with being separated from the line conductor by the sameinterval. A dielectric frame 34 is joined onto the dielectric substrate31 so as to surround the mounting portion 31 a with sandwiching aportion of the line conductor 32 and a portion of each of the cofacialground layers 33. A bottom face ground layer 35 is formed on the bottomface of the dielectric substrate 31 so as to oppose the line conductor32 and the cofacial ground layers 33. Connecting conductor layers 36through which the bottom face ground layer 35 is connected to thecofacial ground layers 33 correspond to the above-mentioned side faceground layers 18, 28.

In the package for housing a high-frequency semiconductor element of theinvention, the thickness d34 of the dielectric frame 34 is larger thanthe thickness d31 of the dielectric substrate 31 (d34>d31), and thewidth of the portion 32 a of the line conductor 32 which is sandwichedbetween the dielectric substrate 31 and the dielectric frame 34 issmaller than the width of the other portion the other portions (i.e. theportions which are in front and in rear of the dielectric frame 34 andin which the line conductor 32 is exposed,) thereby forming a narrowportion 32 a. Projected portions 33 a are disposed in the portions ofthe cofacial ground layers 33 which portions are sandwiched between thedielectric substrate 31 and the dielectric frame 34. The projectedportions are projected toward the narrow portion 32 a of the lineconductor 32 with forming the same interval. In the above embodiment,the input/output feedthroughs are constituted so as to be laterallysymmetric (vertically symmetric in FIG. 1A) with respect to a planewhich includes the cutting plane line IV—IV and orthogonal to the paperplane of FIG. 1A. Alternatively, the in other embodiment of theinvention, the input/output feedthrough may be asymmetrical, that is, itmay becomes that g1≠g2 and g3≠g4.

According to the thus configured package for housing a high-frequencysemiconductor element of the invention, with respect to the portion 32 aof the line conductor 32 in which the width is reduced in order toattain the matching of the characteristic impedance in each of thehigh-frequency input/output feedthroughs by the conventional design, thedielectric frame 34 is thicker than the dielectric substrate 31, and theprojected portions 33 a are disposed in the cofacial ground layers 33which are formed on both the sides of the line conductor 32 with formingthe same interval, so as to be projected toward the portion 32 a of theline conductor 32 with forming the same interval. In the side of thedielectric substrate 31, therefore, the electric field of thehigh-frequency signal is concentrated toward the bottom face groundlayer 35 and the cofacial ground layers 33 as shown in FIG. 2A. In theside of the dielectric frame 34, the transmission of the electric fieldcan be substantially eliminated. The electric field distribution can beshaped into the quasi-TEM mode. In other words, the electric fielddistribution can be made closer to the quasi-TEM mode which is theelectric field distribution like FIG. 2B in the portions of the lineconductor 32 other than the portion 32 a sandwiched between thedielectric substrate 31 and the dielectric frame 34, i.e., the portionswhich are in front and in rear of the dielectric frame 34 and in whichthe line conductor 32 is exposed. As a result, the transmission modes inthe line conductor 32 can be matched with each other. Even when adifference in characteristic impedance occurs in the portion 32 a of theline conductor 32 which is sandwiched between the dielectric substrate31 and the dielectric frame 34, return and insertion losses due to thedifference of the transmission modes are not produced, with the resultthat a package for housing a high-frequency semiconductor element whichis of the so-called ceramic wall type (in the case of ceramic frame 34),which has excellent transmission characteristics for a high-frequencysignal, and which has superior high-frequency characteristics can beobtained.

Terminal electrodes of the high-frequency semiconductor element 63mounted on the mounting portion 31 a, and wiring conductors of externalcircuits are connected to the line conductors 32 via wires or ribbons sothat the high-frequency semiconductor element in the package iselectrically connected to the external circuits. A cover which is madeof the above-mentioned material is attached to the upper face of thedielectric frame 34 by the above-mentioned attaching method. As aresult, the high-frequency semiconductor element 63 is housed in thepackage in a hermetically sealed manner, thereby constituting ahigh-frequency semiconductor device as a product.

In accordance with the specifications of the package, the dielectricsubstrate 31 and the dielectric frame 34 are made of the same dielectricas that of the high-frequency input/output feedthroughs 24. From theviewpoint that the bottom face ground layer 35 is required to be theideal grounded state, it is preferable to form a ground layer on thebottom face of the dielectric substrate 31 in the same manner as thebottom face ground layer 35.

The dielectric substrate 31 and the dielectric frame 34 are joinedtogether by, for example, stacking ceramic green sheets which will berespectively formed into the dielectric substrate 31 and the dielectricframe 34 as a result of firing, and then firing the sheets to beintegrated. The line conductors 32, the cofacial ground layers 33, thebottom face ground layer 35, and the connecting conductor layers 36 areformed so as to cover the dielectric substrate 31, by, for example,applying or embedding conductor paste of a predetermined pattern to thedielectric substrate 31 and then firing the paste so as to be integratedwith the dielectric substrate 31.

In the embodiment, the portion of the dielectric frame 34 whichcorresponds to the upper dielectric substrate 16 of the high-frequencyinput/output feedthrough part is integrated with the dielectric frame 34so that the upper face of the portion is cofacial with that of thedielectric frame 34. According to this configuration, a cover (referencenumeral 50 in above described FIGS. 9 to 11) may be attached to theseupper faces directly or via a frame-like metal seal or the like, therebyenabling the high-frequency semiconductor element mounted on themounting portion 31 a to be housed in the package in a hermeticallysealed manner. As described above, even when a step corresponding to theprojection 49 exists as in above described FIG. 9, there arises noproblem.

The dielectric constant of the portion 34 a corresponding to the upperdielectric substrate (reference numeral 26 described above) may be madedifferent from or, for example, smaller than that of the other portionof the dielectric frame 34, whereby the transmission modes for ahigh-frequency signal can be made further closer as described above.Therefore, the return and insertion losses can be effectively reduced.

The mounting portion 31 a of the dielectric substrate 31 corresponds tothe lower dielectric substrate 15 as shown in FIGS. 1 and 2, themounting portion 34 a of the dielectric frame 34 corresponding to theupper dielectric substrate 16 as shown in FIGS. 1 and 2.

In the embodiment, one high-frequency input/output feedthrough part isdisposed in each of the sides of the dielectric substrate 31,respectively. Alternatively, the input/output feedthrough parts may bedisposed in other positions, or plural input/output feedthrough partsmay be disposed in one side as shown above in FIGS. 10 and 11.

In the package for housing a high-frequency semiconductor element of theinvention also, an upper-face ground layer (see 75 described above)andside face ground layers (see 18 b described above) may be furtherdisposed on the upper and side faces of the dielectric frame 34corresponding to the upper dielectric substrate of each of thehigh-frequency input/output feedthrough parts. When such layers aredisposed, the transmission modes are matched by the functions of thethicknesses of the dielectric substrate 31 and the dielectric frame 34which are vertically stacked, and the projected portions 33 a of thecofacial ground layers 33, so that return and insertion losses can bereduced. Furthermore, this configuration causes the line conductor 32 ato be surrounded by the ground layers, so as to function as a shieldagainst a high-frequency signal.

The bottom face ground layer 35, the connecting conductor layers 36, andthe side face and upper-face ground layers of the dielectric frame 34may be formed as a metal film layer. Alternatively, the layers may beconfigured as a substantially continuous ground layer by arranging anumber of through conductors 61, 62 in the same manner as in FIGS. 12and 13 described above or connecting the conductors, so as to functionin the same manner as a film layer, or by attaching a metal plate or ametal block.

Hereinafter, specific examples of the invention will be described.

EXAMPLE 1

In the embodiment of FIGS. 1 and 2, by using a ceramic forming method inwhich so-called cosintering is conducted by the ceramic green sheetmultilayer technique, the following high-frequency input/outputfeedthrough was produced. The upper dielectric substrate 16 in whichlength×width×thickness is 1.5 mm×1.0 mm×0.2 mm and which is made ofalumina (the specific dielectric constant ∈_(r)=9.8) is Joined onto thelower dielectric substrate 15 in which length×width×thickness is 0.5mm×1.0 mm×0.51 mm and which is made of alumina. The bottom face groundlayer 17 and the side face ground layers 18 which are made of W of athickness of about 10 μm and Ni+Au plating of a thickness of about 2 to6 μm are formed on the lower and side faces of the lower dielectricsubstrate 15. The line conductor 19 made of the same material, and thecofacial ground layers 20 which are disposed on both the sides of theline conductor 19 with being separated from the line conductor 19 by thesame interval are formed on the upper face of the substrate. The widthW19 a of the portion 19 a (narrow portion) of the line conductor 19which is sandwiched between the lower and upper dielectric substrates15, 16 is 0.15 mm, and the width W19 of the other portions 19 b, 19 c,i.e. the portions which are in front and in rear of the upper dielectricsubstrate 16 and in which the line conductor 19 is exposed is 0.20 mm.Projected portions 20 a 1 are disposed in the portions of the cofacialground layers 20 which portions 20 a 1 are sandwiched between the lowerdielectric substrate 15 and the upper dielectric substrate 16. Theprojected portions are projected toward the narrow portion 19 a of theline conductor 19 with forming the same interval. The interval (g1=g2)for the portions is 0.265 mm, and the interval (g3=g4) of the otherportions 19 b, 19 c (i.e. the portions which are in front and in rear ofthe upper dielectric substrate 16 and in which the line conductor 19 isexposed) is 0.30 mm. As a result, a high-frequency input/outputfeedthrough A which is the high-frequency input/output feedthrough ofthe invention was obtained.

As a high-frequency input/output feedthrough of a comparison example, ahigh-frequency input/output feedthrough B was obtained in the samemanner as described above except the followings. Alumina of a thicknessof 0.38 mm is used as the upper dielectric substrate. The width of theportion (narrow portion) of the line conductor which is sandwichedbetween the lower and upper dielectric substrates is 0.08 mm. Noprojected portions are disposed in the portions of the cofacial groundlayers which portions are sandwiched between the lower dielectricsubstrate and the upper dielectric substrate. The interval between theportions and the line conductor (narrow portion) is 0.36 mm.

The high-frequency input/output feedthroughs A and B were applied to aninput/output portion of a package for housing a high-frequencysemiconductor element. The return loss (S₁₁) in the frequency region of0 to 70 GHz was measured by a usual measuring method to obtain thefrequency characteristics of the return loss. Similarly, the amount ofthe insertion loss (S₂₁) was measured in the form of an insertion lossby a usual measuring method as an evaluation index of the transmittedamount in the input signal, thereby obtaining the frequencycharacteristics of the insertion loss. The results of these measurementsare shown in the graphs of FIGS. 5 and 6. FIG. 5 shows the frequencycharacteristics of the return loss, and FIG. 6 shows the frequencycharacteristics of the insertion loss. In FIG. 5, the abscissa indicatesthe frequency (unit: GHz), the ordinate indicates the return loss S₁₁(unit: dB), and the characteristic curves of the high-frequencyinput/output feedthroughs A and B are indicated by the solid line andthe broken line, respectively. In FIG. 6, the abscissa indicates thefrequency (unit: GHz), the ordinate indicates the insertion loss S₂₁(unit: dB), and the characteristic curves of the high-frequencyinput/output feedthroughs A and B are indicated by the solid line andthe broken line, respectively.

From the results shown in FIGS. 5 and 6, it will be seen that, in thehigh-frequency input/output feedthrough B, excellent high-frequencycharacteristics were observed in the frequency range lower than 40 GHzbut the characteristics are remarkably impaired in the millimeter waveregion, particularly in the frequency range higher than 40 GHz. Bycontrast, it will be seen that, in the high-frequency input/outputfeedthrough A, excellent return and transmission characteristics wererealized even in the frequency range higher than 40 GHz because thetransmission modes in the line conductor are matched with each other.

From the above, it was ascertained that, in the high-frequencyinput/output feedthrough of the invention, return and insertion lossesdue to a difference of the transmission modes are reduced and excellenttransmission characteristics for a high-frequency signal can beobtained.

FIG. 14 is a perspective view of a high-frequency input/outputfeedthrough 65 of still another embodiment of the invention, and FIG. 15is a plane view of the high-frequency input/output feedthrough 65. Thehigh-frequency input/output feedthrough 65 shown in FIGS. 14 and 15 issimilar to the input/output feedthrough described above in relation toFIGS. 1 and 2, and corresponding elements are denoted by the samereference numerals. On the lower dielectric substrate 15, the elongatedline conductor 19 is formed, and the cofacial ground layer 20 is formedat each side in the longitudinal direction of the line conductor 19. Inthe lower dielectric substrate 15, a notch 66 is formed at each positioncorresponding to the cofacial ground layer 20 along the longitudinaldirection of the line conductor 19. On an inner circumference of thenotch 66, a conductive layer which is electrically connected with thecofacial ground layer 20 is formed. On the lower dielectric substrate15, the upper dielectric substrate 16 is formed across the lineconductor 19 and the cofacial ground layer 20.

The electric field distribution of the input/output feedthrough shown inFIGS. 14 and 15 is shown in FIGS. 16A and 16B. FIGS. 16A and 16Bcorresponds to above FIGS. 2A and 2B, respectively. The electric fielddistribution shown in FIG. 16A shows a transmission mode in which thetransmission mode formed at the joint portion between the lowerdielectric substrate 15 and the upper dielectric substrate 16 is closeto the quasi-TEM mode, and approximates to the quasi-TEM mode at theportion of the lower dielectric substrate 15 in which the upperdielectric substrate 16 is not formed, as shown in FIG. 16.

FIG. 17 is an exploded perspective view showing an entire constitutionof a semiconductor device using the input/output feedthrough 65 shown inFIG. 14 which is simplified, and FIG. 18 is a longitudinal section viewof the same. This embodiment is similar to the embodiment shown in FIGS.3 and 4, and the corresponding elements are denoted by the samereference numerals. On the metal substrate 21, the frame 22 made ofdielectric is disposed, and at the feedthrough attaching portion 23 ofthe frame 22, the input/output feedthrough 65 is disposed. Further,lines 67, 68 for transmitting direct current power and direct currentsignal are disposed in the frame 22. The semiconductor element 63 isattached on the substrate 21 in the frame 22. The semiconductor element63 is connected to the input/output feedthrough 65. The semiconductorelement 63 may be MMIC (Microwave Monolisic Integrated Circuit), forexample. Other constitutions are similar to those of the above-mentionedembodiments.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and the rangeof equivalency of the claims are therefore intended to be embracedtherein.

What is claimed is:
 1. A package for housing a high frequencysemiconductor element comprising: a substrate made of a dielectric ormetal, having one surface including a mounting portion on which thehigh-frequency semiconductor element is mounted; a frame made of adielectric or metal, joined to the substrate so as to enclose themounting portion, the frame being notched to form an input/outputfeedthrough mounting portion whose side faces and bottom face areelectrically conductive; a high-frequency input/output feedthroughfitted to the input/output feedthrough mounting portion; and a capattached to a top face of the frame, wherein the high-frequencyinput/output feedthrough comprising: a) a first dielectric substrate; b)a high-frequency transmission line of narrow width extending on a firstsurface of the first dielectric substrate, the high-frequencytransmission line having a first high-frequency transmission lineportion and second high-frequency transmission line portions extendingfrom both longitudinal ends of the first high-frequency transmissionline portion, respectively; c) a pair of first ground conductors ofnarrow width extending on the first surface of the first dielectricsubstrate, the first ground conductors being spaced from both widthdirection sides of the high-frequency transmission line, respectively,each of the first ground conductors having a first ground conductorportion extending along the first high-frequency transmission lineportion and second ground conductor portions extending from bothlongitudinal ends of the first ground conductor portion along the secondhigh-frequency transmission line portions respectively; d) a seconddielectric substrate for hermetic sealing, overlaid on the first surfaceof the first dielectric substrate so as to cover the firsthigh-frequency transmission line portion and the first ground conductorportions; and e) a second ground conductor formed on a second surface ofthe first dielectric substrate opposite the first surface thereof, thesecond ground conductor overlapping a region including thehigh-frequency transmission line, the first ground conductors, and gapshaving widths between the high-frequency transmission line and the firstground conductors when viewed in a direction perpendicular to the firstsurface of the first dielectric substrate, the second ground conductorconstituting first line means together with the first high-frequencytransmission line portion, the first ground conductor portions and thefirst and second dielectric substrates and constituting second linemeans together with the second high-frequency transmission line portion,the second ground conductor portions and the first dielectric substrate,wherein: f) a first width of the first high-frequency transmission lineportion is smaller than a second width of the second high-frequencytransmission line portions, g) a thickness of the second dielectricsubstrate is selected to be larger than a thickness of the firstdielectric substrate, and the first width and the regions between thefirst high-frequency transmission line portion and the first groundconductors are selected so that a characteristic impedance of the firstline means is smaller than a characteristic impedance of the second linemeans, in order to make approximation of a transmission mode of thefirst line means to a transmission mode of the second line means.
 2. Thepackage for housing a high-frequency semiconductor element of claim 1,wherein a first distance between the first ground conductor portions onboth sides of the first high-frequency transmission line portion in thewidth direction of the first ground conductor portions is equal to orsmaller than a second distance between the second ground conductorportions on both sides of the second high-frequency transmission lineportion.
 3. The package for housing a high-frequency semiconductorelement of claim 1 or 2, wherein the first width and first gaps in thehigh-frequency input/output feedthrough are selected so that a ratio ofthe characteristic impedance of the first line means to thecharacteristic impedance of the second line means meets the followingrelationship: 0.5≦Z19 a/Z19≦0.9.
 4. A package for housing a highfrequency semiconductor element comprising: a substrate made of adielectric or metal, having one surface including a mounting portion onwhich the high-frequency semiconductor element is mounted; a frame madeof a dielectric or metal, joined to the substrate so as to enclose themounting portion, the frame being notched to form an input/outputfeedthrough mounting portion whose side faces and bottom face areelectrically conductive; a high-frequency input/output feedthroughfitted to the input/output feedthrough mounting portion; and a capattached to a top face of the frame, wherein the high-frequencyinput/output feedthrough comprising: a first dielectric substrate havingone surface where a line conductor and cofacial ground layers spaced ata same distance from both sides of the line conductor are formed, theother surface where a bottom face ground layer is formed, and side faceswhere side ground layers are formed; and a second dielectric substratejoined to the one surface of the first dielectric substrate so as tosandwich portions of the line conductor and the cofacial ground layersbetween the first and second substrates, wherein the second dielectricsubstrate i s made thicker than the first dielectric substrate, theportion of the line conductor sandwiched between the first and secondsubstrates is made narrower than the other portions thereof in width,and the portions of the cofacial ground layers sandwiched between thefirst and second substrates project toward the line conductor uniformlyin a longitudinal direction of the line conductor so as to be spaced ata same distance from both sides of the line conductor.
 5. The packagefor housing a high-frequency semiconductor element of claim 4, whereinthe first dielectric substrate of the high-frequency input/outputfeedthrough has a dielectric constant ∈_(r)15 and a thickness, and athickness of the second dielectric substrate having a dielectricconstant ∈_(r)16 is ∈_(r)15/(2∈_(r)16) or more times the thickness ofthe first dielectric substrate.
 6. The package for housing ahigh-frequency semiconductor element of claim 4, wherein the thicknessof the second dielectric substrate of the high-frequency input/outputfeedthrough is ∈_(r)15/(∈_(r)16) or more times the thickness of thefirst dielectric substrate.
 7. The package for housing a high-frequencysemiconductor element of claim 1 or 4, wherein heights of theprojections toward the line conductor of the high-frequency input/outputfeedthrough, of the portions of the cofacial ground layers sandwichedbetween the first and second dielectric substrates or the gaps betweenthe line conductor and the cofacial ground layers are ∈_(r)15/(2∈_(r)16)or less times the thickness of the first dielectric substrate.
 8. Thepackage for housing a high-frequency semiconductor element of claim 1 or4, wherein the dielectric constant ∈_(r)15 of the first dielectricsubstrate of the high frequency input/output feedthrough is smaller thanthe dielectric constant ∈_(r)16 of the second dielectric substrate. 9.The package for housing a high-frequency semiconductor element of claim1 or 4, wherein an upper ground layer of the high-frequency input/outputfeedthrough is provided on a surface of the second dielectric substrateof an opposite side to the first dielectric substrate, and side groundlayers are provided on side faces of the second dielectric substrate.10. The package for housing a high-frequency semiconductor element ofclaims 1 or 4, wherein the first and second dielectric substrate of thehigh-frequency input/output feedthrough are made of one or morematerials selected from the group consisting of alumina, mullite, glassceramics, polytetrafluoroethylene (PTFE), glass epoxy resins andpolyimides.
 11. The package for housing a high-frequency semiconductorelement of claim 1 or 4, wherein the line conductor and the cofacialground layers of the high-frequency input/output feedthrough are made ofone or more materials selected from the group consisting of Cu,MoMn+Ni+Au, W+Ni+Au, Cr+Cu, Cr+Cu+Ni+Au, Ta₂N+NiCr+Au, Ti+Pd+Au, andNiCr+Pd+Au.
 12. A package for housing a high-frequency semiconductorelement comprising: a dielectric substrate having one surface includinga mounting portion on which the high-frequency semiconductor element ismounted; a line conductor formed from a proximity of the mountingportion to a proximity of a periphery of the dielectric substrate on theone surface of the dielectric substrate; first ground layers arrangedfrom a proximity of the mounting portion to a proximity of a peripheryof the dielectric substrate on the one surface of the dielectricsubstrate so as to be spaced at a same distance from both sides of theline conductor; a dielectric frame joined to the one surface of thedielectric substrate so that the mounting portion is enclosed by thedielectric frame and portions of the line conductor and the first groundlayers are sandwiched between the dielectric substrate and thedielectric frame; a second ground layer formed on the other surface ofthe dielectric substrate; and a connecting conductor layer forconnecting the second ground layer to the first ground layers, whereinthe dielectric frame is made thicker than the dielectric substrate, theportion of the line conductor sandwiched between the dielectricsubstrate and the dielectric frame is made narrower than the otherportions thereof in width, and the portions of the first ground layerssandwiched between the dielectric substrate and the dielectric frameproject toward the line conductor so as to be spaced at a same distancefrom both sides of the line conductor uniformly in a longitudinaldirection of the line conductor.
 13. The package for housing ahigh-frequency semiconductor element of claim 12, wherein the dielectricsubstrate has a dielectric constant ∈_(r)15 and a thickness, and athickness of the dielectric frame having a dielectric constant ∈_(r)16is ∈_(r)15/(2∈_(r)16) or more times the thickness of the dielectricsubstrate.
 14. The package for housing a high-frequency semiconductorelement of claim 12 or 13, wherein the thickness of the dielectric frameis ∈_(r)15/(∈_(r)16) or more times the thickness of the dielectricsubstrate.
 15. The package for housing a high-frequency semiconductorelement of claim 12 or 13, wherein heights of the projections toward theline conductor, of the portions of the first ground layers sandwichedbetween the dielectric substrate and the dielectric frame, or the gapsbetween the line conductor and the first ground layers are∈_(r)15/(2∈_(r)16) or less times the thickness of the first dielectricsubstrate.
 16. The package for housing a high frequency semiconductorelement of claim 12 or 13, wherein the dielectric constant ∈_(r)15 ofthe dielectric substrate is smaller than the dielectric constant ∈_(r)16of the dielectric frame.
 17. The package for housing a high-frequencysemiconductor element of claim 12 or 13, wherein an upper ground layeris provided on a surface of the dielectric frame of an opposite side tothe dielectric substrate, and side ground layers are provided in aninterior of the dielectric frame above the connecting conductor layer.18. The package for housing a high-frequency semiconductor element ofclaim 12 or 13, wherein the dielectric substrate and the dielectricframe are made of one or more materials selected from the groupconsisting of alumina, mullite, glass ceramics, polytetrafluoroethylene(PTFE), glass epoxy resins and polyimides.
 19. The package for housing ahigh-frequency semiconductor element of claim 12 or 13, wherein the lineconductor and the first ground layers are made of one or more materialsselected from the group consisting of Cu, MoMn+Ni+Au, W+Ni+Au, Cr+Cu,Cr+Cu+Ni+Au, Ta₂N+NiCr+Au, Ti+Pd+Au, and NiCr+Pd+Au.
 20. Ahigh-frequency semiconductor apparatus comprising: a semiconductorelement installed in a space on the dielectric substrate of the packagefor housing a high-frequency semiconductor element of claim 1, 4 or 12,enclosed by the frame, the semiconductor element being electricallyconnected to the input/output feedthrough for high-frequency.